1. Field of the Invention
The present invention pertains generally to a medical device useful for delivering a substance to a biological passageway. More specifically, the present invention pertains to a catheter device having a syringe assembly useful for delivering a therapeutic or bioactive substance to a passageway, such as a blood vessel.
2. Description of the Background
Percutaneous transluminal coronary angioplasty (PTCA) is a procedure for treating heart disease. A catheter assembly having a balloon portion is introduced percutaneously into the cardiovascular system of a patient via the brachial or femoral artery. The catheter assembly is advanced through the coronary vasculature until the balloon portion is positioned across the occlusive lesion. Once in position across the lesion, the balloon is inflated to a predetermined size to radially press against the atherosclerotic plaque of the lesion for remodeling of the blood vessel wall. The balloon is then deflated to a smaller profile to allow the catheter to be withdrawn from the patient""s vasculature.
Restenosis of the artery commonly develops over several months after the procedure, which may require another angioplasty procedure or a surgical by-pass operation. Restenosis is thought to involve the body""s natural healing process. Angioplasty or other vascular procedures injure the vessel walls, removing the vascular endothelium, disturbing the tunica intima, and causing the death of medial smooth muscle cells (SMCs). Excessive neoinitimal tissue formation, characterized by SMC migration and proliferation to the intima, follows the injury. Proliferation and migration of SMCs from the media layer to the intima cause an excessive production of extra cellular matrices (ECM), which is believed to be one of the leading contributors to the development of restenosis. The extensive thickening of the tissues narrows the lumen of the blood vessel, constricting or blocking blood flow through the vessel.
To reduce the chance of the development of restenosis, therapeutic substances are administered to the treatment site. For example, anticoagulant and antiplatelet agents are commonly used to inhibit the development of restenosis. In order to provide an efficacious concentration to the target site, systemic administration of such medication often produces adverse or toxic side effects for the patient. Local delivery is a preferred method of treatment in that smaller total levels of medication are administered in comparison to systemic dosages, but are concentrated at a specific site. Local delivery, thus, produces fewer side effects and achieves more effective results.
One commonly applied technique for the local delivery of a therapeutic substance is through the use of a medicated, implantable prosthesis, one example of which includes a stent. A stent coated with a polymeric carrier, which is impregnated with a therapeutic substance, can be implanted at a selected site of treatment. The polymeric carrier allows for a sustained delivery of the therapeutic substance. A disadvantage associated with the use of a medicated stent is that the quantity of the substance that can be impregnated in the polymeric carrier is limited. Increasing the quantity of the substance in the polymeric coating can lead to processing difficulties such as poor adhesion of the coating to the stent surface. In order to increase the capacity of the polymeric carrier, the amount of polymeric material employed, and in effect the thickness of the coating, must be increased to accommodate the quantity of the substance used. An increase in the quantity of the polymeric material and the profile of the coating can perturb the geometrical and mechanical functionality of the stent, as well as limit the applications for which the stent can be used.
Another disadvantage associated with the use of medicated stents is that the polymeric carrier is only capable of applying the therapeutic substance to the inner surface of the tunica intima layer of the vessel. The polymeric carrier is incapable of significantly introducing a therapeutic substance to the tunica adventitia or the tunica media layers of the vessel. There is a need to provide a substance delivery apparatus which is capable of applying any desired amount of therapeutic substances to the tunica adventitia and media layers to inhibit migration of SMCs and the development of ECM.
Another commonly applied technique for the local delivery of a therapeutic substance is through the use of a porous balloon attached to a distal end of a catheter assembly. The expansion of the balloon, which in effect results in the dilation of the occluded region, is accomplished by injecting a therapeutic substance into the balloon. The use of a therapeutic substance as an expansion fluid additionally functions as a medicament for the diseased region, as the therapeutic substance is discharged from the porous balloon during and subsequent to the expansion therapy. A shortcoming associated with this procedure is that the therapeutic substance is contiguously carried off in the patient""s blood steam as it is being discharged from the balloon, which results in an ineffective treatment of the target site and adverse exposure of the substance to healthy tissues. There is a need for a substance delivery apparatus that is capable of applying a therapeutic substance to the diseased region without significant loss of the substance caused by the downstream flow of blood.
In accordance with one aspect of the present invention, a substance delivery apparatus for a catheter assembly is provided which includes a base supported by the catheter assembly and a needle pivotally connected to the base. The needle is used for penetrating into tissues of a passageway for administering a bioactive or therapeutic substance or combination of substances. A coupling element, for example a pin element, pivotally connects the base to the needle. The substance delivery apparatus can additionally include a delivery lumen in fluid communication with the needle. A bioactive or therapeutic substance or a combination of substances can be introduced into the delivery lumen for injection out from the needle. In accordance with one embodiment, the base is made from a hollow tube having a pair of opposing slots cut out at one end of the tube to define an opposing pair of flanges. A portion of one end of the needle, accordingly, can be disposed between and connected to the flanges.
In accordance with one embodiment, the catheter assembly includes a membrane having a pair of opposing ends coupled to a distal end of the catheter assembly to form a chamber. The chamber is in fluid communication with the catheter assembly to allow the membrane to be inflated to an expanded configuration. The membrane can include a first section and a second section. The second section of the membrane can have a thickness less than the thickness of the first section such that when the membrane is inflated, the second section expands outwardly to a greater extent than the first section. The first section can support the base and the second section can cause the needle to pivotally rotate about the coupling element for penetration into tissues of a passageway.
In accordance with one embodiment, the first section of the membrane can include pores. The membrane can additionally include a third section having pores, in addition to or in lieu of a porous first section. The pores can allow for the discharge of a bioactive or therapeutic substance that is introduced into the chamber of the expandable membrane.
In accordance with yet another embodiment, the substance delivery apparatus can additionally include a transport element operably supported by the catheter assembly. The transport element can have a first electrode element, a second electrode element, and a power supply electrically communicating with the first and second electrode elements. Alternatively, the transport element can be an ultrasonic transducer.
In accordance with another aspect of the present invention, a device for delivering a substance to a desired area of a passageway is provided. The device includes a catheter assembly having a distal end and a proximal end. A membrane having a pair of opposing ends is coupled to the distal end of the catheter assembly to form a chamber. The membrane can be inflated from a collapsed configuration to an expanded configuration. A first syringe assembly is supported by the catheter assembly for allowing a first therapeutic substance to be injected into a tissue of a passageway. The first syringe assembly includes a base, a needle pivitolly coupled to the base, and a hinge member pivitolly coupling the base to the needle. The needle is capable of pivoting from a first position towards a second position in response to the membrane being inflated from the collapsed configuration to the expanded configuration. The needle of the first syringe assembly can also be capable of pivoting from the second position back towards the first position in response to the membrane being deflated. The needle of the first syringe assembly can be configured to penetrate into the tunica media layer of a blood vessel wall for administering the first therapeutic substance to a region of the tunica media layer of the blood vessel wall.
In accordance with one embodiment, the membrane can include a plurality of pores for allowing a second therapeutic substance supplied into the chamber to be discharge out from the pores. The second therapeutic substance can be the same as or different than the first therapeutic substance.
The device can additionally include a second syringe assembly supported by the catheter assembly for allowing a third therapeutic substance to be injected into a tissue of the passagewayxe2x80x94the third therapeutic substance being the same as or different than the first therapeutic substance. The second syringe assembly includes a base, a needle pivotally coupled to the base of the second syringe assembly, and a hinge member pivitolly coupling the base to the needle of the second syringe assembly. The needle for the second syringe assembly is capable of pivoting from a first position towards a second position in response to the membrane being inflated from the collapsed configuration to the expanded configuration. The needle of the first syringe assembly can also be capable of pivoting from the second position back towards the first position in response to the membrane being deflated.